User Manual

Operating Brushless Motors
Advanced Digital Motor Controller User Manual 125
Closed Loop Modes in Sensorless
Closed loop speed mode can be used with sensorless motors. The speed is determined
by measuring the time between commutations. Sensorless motors will work the same as
sensored motors and require similar PID tuning. The only limitation is at very slow speed
where the motor cannot be made to go slower than the RPM resulting from the Startup
Frequency parameter.
Position modes, and the Speed Position modes cannot be used reliably with sensorless
motors.
Operating Brushless Motors
This section covers operating features that are common to Brushless Motor control, re-
gardless of the commutation mode.
Once configured and tuned, a brushless motor can be operated exactly like a DC motor
and all other sections in this manual are applicable. In addition, the Hall sensors or encod-
ers, provide extra information about the motor’s state compared to DC motors. This infor-
mation enables the additional features discussed below.
Stall Detection
The rotor sensors and the encoders can be used to detect whether the motor is spinning
or not. The controller includes a safety feature that will stop the motor power if no rotation
is detected while a given amount of power is applied for a certain time. Three combina-
tions of power and time are available:
• 250ms at 10% power
• 500ms at 25% power
• 1s at 50% power
If the power applied is higher than the selected value and no motion is detected for the
corresponding amount of time, the power to the motor is cut until the motor command is
returned to 0. This function is controlled by the BLSTD - Brushless Stall Detection param-
eter (see “BLSTD - Brushless Stall Detection” in Command Reference section). Do not
disable the stall protection.
A stall condition is indicated with the “Stall” LED on the Roborun PC utility screen.
In Trapezoidal modes using Hall sensors, the Stall detection looks for changes at any of
the Hall sensors inputs. In Sinusoidal modes, the detection uses the speed measurement
from the rotor sensor.
Important Notice
In close loop modes, it is quite possible to have the motor stopped while power is
applied to them. That could happen while stopped uphill, for example. Select the
appropriate triggering level for your application